Having trouble with backgear

I have a 16" 1926 south bend, and I cant understand how to engage the back gear. I haven't never needed to use it, but would like to know how. I have tried engaging it, but it just locks the spindle and wont allow it to turn.
My next question is about a little knob that disengages the cones from driving the spindle. If you put you right hand on the chuck and your left on te first cone of the flat belt it will be in the middle. My slides down every now and then, this kinda disables the spindle and the cone. Whats its purpose and what makes it stay up. A spring or was it once threaded and just stripped out.
Chris

Chris, You are right when you pull up the lever on the Back Gear Quill it locks the spindle. The little knob may be stripped, mine just pulls out and stays but yours is an older model so it may be threaded...Bob

To clarify - the two are related. The pin that is giving you a little trouble has to be disengaged when the back gears are engaged. When the pin is disengaged, as you have found, the cone pulley is free to turn on spindle (at least if you lube it thru the little set screw oil ports in the cone steps every now and then)

When you then engage the back gears, the spindle will not be locked up, and the cone will go fast while the spindle goes slow. Magic.

John

Thanks aametalmaster and John! What makes the little nob stay up on the one's you fellas have seen. John, you know alot about this old machinary. Are you a student of fine old machinary or just from that era You seem knowledable enough to write a book on it.
Thanks
Chris

Hi Chris:

I am , well, old First ran a rickety old SB in the basement shop at Waco High School in 1955.

Owned a twenties Series "O" 13 X 5 as my first lathe in '66

Collected information and read everything I could.

Ended up designing machinery and equipment as a career.

Retired now, still very much in the old iron mode, but also in to trying my hand at CNC.

John

My three SB's - 1913 13", 1920 16" and 1923 11" all have a square head bolt on the face of the bull gear that rides in a slot and clamps a key behind the bull gear that engages / disengages the spindle cone pulley to/from the bull gear.

Engaged in the outermost position, disengaged in the inner most position.

At some later time, 1926 - 1927 ?, SB changed to a spring loaded pin moving the key to more conveniently serve the same function.

In either case, it would be worthwhile to remove the spindle, carefully noting location and number of shims that may be under the bearing caps, to inspect the key or pin and their point of engagement for damage and repair if necessary. It is NOT necessary to remove the gear off the back end of the spindle to perform this inspection as the cone pulley can be slid back far enough on the spindle to see the parts in question. This effort could well prevent more serious damage !

Jim C.

Chris:

On further study, likely that the spring is weak or broken. Also the detents on the face of the bull gear may be worn.

Let us know what you find.

Jim C.